Gems, Metal, and Earth’s Core

The Fire of Australia, a whacking great chunk of opal, isn’t particularly interesting from a ‘science’ viewpoint.

But I’m human, which is probably why anything big and shiny gets my attention: including that rock.

Wrenching myself back on-topic, scientists found a stream of liquid metal flowing at the edge of Earth’s core. Studying it may help us learn why Earth’s magnetic field flip-flops at apparently-irregular intervals. What we’ll learn is beyond me: we didn’t know much about geomagnetic reversal when I started school.

We still don’t, for that matter. As I keep saying, there is a very great deal left to learn.

‘Once it Was Believed, Now We Know’

Back in my ‘good old days,’ scientists were getting past the notion that Neanderthals were “cavemen,” and I’ve talked about that before. (January 13, 2017; September 23, 2016)

I don’t know how often the “once it was believed, now we know” phrase popped up; but the science-related stuff I read often had a triumphalist tone. That was morphing into the currently-fashionable ‘and we’re all gonna die’ attitude during my youth, which was well-established the last time I did time in academia.

I think both assumptions make about as much sense as believing that using the brains God gave us offends the Almighty.

Recapping what I’ve said before: acting like humans is okay.

We’re supposed to be curious. A thirst for truth and happiness is written into each of us. If we’re doing our job right, the search will lead us to God. (Catechism of the Catholic Church, 27)

Seeking the Almighty and studying this wonder-filled universe is part of being human. (Catechism, 35, 50, 159, 2292–2296)

So does having hysterics over an impending environmental apocalypse. Some folks still apparently take Ehrlich’s prognostications seriously. I don’t. (August 12, 2016 )

I do think Earth’s climate is changing: and has been ever since our home formed, some 4,540,000,000 years back; give or take 50,000,000. I’d be astonished if it stopped changing during my lifetime.

I also think what we’ve been doing for the last 11,500 years has had an increasingly noticeable effect, at least on a regional level.

Developing industrial processes made a difference. I showed a global map of nitrogen dioxide levels last week.

But I don’t think this is a good time to try taking control of Earth’s climate. Not on a global level.

In my considered opinion, we don’t know nearly enough to do that safely. Not yet. (January 20, 2017)

Good grief: a few centuries back, it looked like the universe might be no more than a few thousand years old. Nobody suspect that the Solar wind existed until 1859, and the jury’s still out on exactly how Solar activity affects Earth’s climate.

We didn’t know for sure that Earth’s continents have been moving around until I was an adult. That may have helped the current ice age get started: but again, we’re not really sure. Not yet.

It’s not that I think Earth never changes, or that we’re helpless to do anything about our home’s environment. But experimenting with geoengineering should probably wait until we know what we’re doing.

1. The Fire of Australia Changes Hands

(From South Australian Museum, via BBC News, used w/o permission.)
(“The Fire of Australia is now on display in South Australia”
(BBC News))

“The world’s finest uncut opal has mostly been kept in a safe deposit box since it was unearthed from the South Australian outback with a pick and shovel 70 years ago.

“Walter Bartram was prospecting in dusty terrain in Coober Pedy, about 750km (466 miles) north of Adelaide, in 1946 when he staked a claim to what became called the Fire of Australia.

“Although his family achieved success in opal trading, their greatest discovery has been seen rarely by the public.

“That has just changed.

“The 998g (35.2oz) opal, valued at nearly A$900,000 (£550,000; $680,000), is now on display in Adelaide’s South Australian Museum….”

Folks who care about such things call opal a mineraloid, not a mineral, since it’s an amorphous solid, not crystalline. It’s a hydrated amorphous form of silica, with water content from 3 to 21% by weight — generally between 6 and 10%.

Don’t bother trying to remember that. There will not be a test on this.

Opals are good for looking at. My language’s word for the stone, “opal,” comes from Latin “opalus.” Romans got that word from Sanskrit “úpala,” probably.

“Opalus” might have come from Ops, the wife of Saturn and goddess of fertility. Part of the Roman Saturnalia — think a major spring break blowout for adults — devoted to Ops was called “Opalia.” Again, you won’t be tested on this.

Maybe “opalus” came from ancient Greek “opallios.” That word meant something like “seeing,” which is where we get “opaque”; it also meant “other” as in “alias” and “alter.” The ancient Greek origin isn’t likely, academics say; but a Sanskrit origin is.

That sort of thing fascinates me. Your experience may vary.

Getting a Grip About Opals and Luck

(From Photo by Ray Bartram/the Bartram family, via The Jewellery Editor, used w/o permission.)
(“The Fire of Australia, discovered by the Bertram family in 1946, is the most valuable piece of rough light opal of its size in the world, weighing approximately 5,000 carats.”
(The Jewellery Editor))

Folks have enjoyed looking at opal for millennia, particularly after giving the rocks a nice polish. Opals were considered lucky — good and bad, depending on which tradition you dip into.

Sir Walter Scott’s “Anne of Geierstein” featured a magic opal with lethal properties. That tale apparently cut the sale of opals in the English-speaking world in half for something like two decades.1

About opals, lucky/unlucky stones, and such things — I have an agate, a geode, a half-dozen California Raisins from a Hardee’s promotion on my desk. They’re there because I think they look nice.

If I thought they magically help me write, or guard my computer’s hard drive, or something like that, I’d have a problem.

Superstition and magic are bad ideas. I don’t mean ‘take a rabbit out of my hat’ stage magic. That’s about as “magical” as me making letters appear on a glowing screen, by twiddling my fingers over a keyboard.

Now that I think of it, maybe that helps explain why some folks are scared of computers, and that’s another topic.

Superstition feels a bit like religion. It can affect worship if someone gets the idea that prayer, for example, depends on ‘going through the motions.’ It’s a bad idea. So is trying to tame occult powers or thinking ‘magic’ charms make sense. (Catechism, 2110–2111, 2117)

2. Iron ‘Jet Stream’

(From ESA, via BBC News, used w/o permission.)
(“Artwork: A depiction of where the jet is moving – in the outer core. The Swarm satellites fly a few hundred km above the planet and sense its magnetic field”
(BBC News))

“This trio of spacecraft are currently mapping Earth’s magnetic field to try to understand its fundamental workings….”

Magnetic north, the point on Earth’s surface where the planet’s magnetic field lines are vertical, was near the rotational pole when Thales of Miletus noticed that lodestones attract iron.

Folks started using lodestones for navigation during the Song Dynasty, about a thousand years back. Being able to navigate between ports is important, so folks have been keeping track of magnetic declination ever since.

We learned that the magnetic pole moves around. It’s been drifting west since about 1400. It had been drifting eastward for about four centuries before that. We call the drift “secular variation, which brings me back to the satellites and those scientists.

A “Jet of Liquid Iron,” Krakatoa, and Jet Streams

“Fast-flowing” is a relative term.

“…’This jet of liquid iron is moving at about fifty kilometres per year,’ explained Dr Chris Finlay from the National Space Institute at the Technical University of Denmark (DTU Space).

“‘That might not sound like a lot to you on Earth’s surface, but you have to remember this a very dense liquid metal and it takes a huge amount of energy to move this thing around…’….”
(Jonathan Amos, BBC News)

About jet streams, Wiley Post often gets credit for discovering Earth’s jet streams, since he noticed his ground speed was higher than the air speed in certain places. The story is a bit more complicated, though.

L. L. Zamenhof put Esperanto together in the 1870s and 1880s. Having a common world language is, I think, a good idea. Mandarin would be a pretty good choice these days, except just about everyone who understands it lives in China.

Inventing one and then trying to get folks who aren’t language geeks to go along with the idea — didn’t work out so well. And that’s yet another topic.

Moving Metal and Questions

These scientists figure that the moving metal stream is about 420 kilometers, 261 miles, wide; and wraps halfway around the planet. How deep it is — is a good question.

They figure it’s the boundary between two parts of Earth’s core. If they’re right, liquid iron approaching the boundary from both sides gets squeezed out sideways; forming the jet, which moves along the tube-shaped boundary.

They don’t have enough data to be sure, but their math suggests that the tube could extend all the way through to the core’s other side, in Earth’s southern hemisphere.

Learning more about this ‘jet stream’ and the rest of Earth’s core should help us understand how Earth’s magnetic field works.2 That, I think, could be very important.

Now, a scary headline from days gone by.

Magnetic Field Reversals

(From NASA, via Wikimedia Commons, used w/o permission.)
(“NASA computer simulation … The tubes represent magnetic field lines, blue when the field points towards the center and yellow when away. The rotation axis of the Earth is centered and vertical. The dense clusters of lines are within the Earth’s core.”
(Wikipedia))

It’s been about a century since scientists like Motonori Matuyama started finding evidence that “magnetic north” wasn’t always near the north pole. Other scientists didn’t get the memo, or weren’t interested.

Lawrence Morley eventually got credit for his explanation of seafloor spreading, but editors working for Nature and Journal of Geophysical Research hadn’t felt like publishing it at the time.

Geomagnetic Reversal, Magnetoreception: Still Learning

The magnetic stripes form when particles in iron-rich rock welling up at mid-ocean ridges ‘freezes’ in line with Earth’s magnetic field.

This gives scientists a pretty good record of field reversals for the last 180,000,000 years. That’s the age of Earth’s oldest existing seafloor. The rest has long since been recycled back into the interior.

I’ve read that Earth’s magnetic field reversals happen at “random” intervals. My guess is that there’s a pattern to Earth’s magnetic field reversals, but scientists haven’t found it yet.

How much time passes between reversals has changed: a lot.

Field reversals started coming closer together a bit upwards of 80,000,000 years back, after a long comparatively-stable patch. There was another fast-changing period about 120,000,000 to 160,000,000 years ago.

A few times 10,000,000 years have gone by with no reversals. Earth’s field flip-flopped five times in a million years about 72,000,000 years back, and the Laschamp event, some 41,400 years back — give or take 2,000 ‐ only lasted a few centuries.

Something causes those reversals, and scientists have come up with a few explanations: but none that match available data.3

The idea that mass extinctions happened during field reversals looked good: except there isn’t a particularly good correlation between the two phenomena.

The reversals probably affect critters that use magnetic fields for navigation, like homing pigeons. How magnetoreception works another mystery.4

On the other hand, considering that we didn’t know about that sense just a few decades back: we’re not doing too badly.

One of those two got the numbers wrong for Earth and our moon’s density.

Assuming that Earth is much less dense than our moon — it’s not — Halley said Earth could be hollow shell about 500 miles thick, with two more shells inside.

He used the diameters of Venus, Mars, and Mercury to define the inner shells, which makes a nifty picture. There’s a sort of elegance to the notion of nested shells inside Earth, whose diameters match other Solar planets.

But it’s not how reality works.

Maybe because a hollow Earth figures in folklore and mythologies, the idea hasn’t gone away.

There’s More to Learn

At the moment, the world’s deepest mine is four kilometers deep. The deepest borehole is still the Kola Superdeep Borehole, reaching 12.262 kilometers below Earth’s surface in 1989. That’s part-way through Earth’s crust.

Folks are still trying to get samples of material from the next layer under Earth’s crust, the mantle:

The last I heard, opinion is divided on whether Earth’s inner core is solid, or plasma that’s dense as a solid. It’s possible — this is even less certain and more debatable — that our planet’s core is a single huge iron crystal.5

This is not the world I grew up in. It’s a great deal more interesting. For the most part I like living in ‘the future,’ and that’s still another topic.

4. Diamonds From Liquid Metal

(From Nemesis International DMCC/Donald Woodrow photographer, via Science, used w/o permission.)
(“Tiny blobs of material trapped inside large, clear diamonds (such as this one) as they formed suggest the gems formed within pockets of liquid metal deep within Earth.”
(Science))

“Some of the most prized diamonds on Earth are unusually clear, exceedingly rare, and often extraordinarily large. Researchers have long wondered how such gems formed, but they’ve been hard to study because they’ve typically ended up on ring fingers rather than under a microscope. Now, a new analysis of imperfections trapped within the diamonds provides the first direct evidence that they were forged within blobs of liquid metal hundreds of kilometers below Earth’s surface….”

Hundreds of kilometers down is still a long way from Earth’s core, but it’s closer than hat borehole: and these are actual samples from Earth’s interior, not laboratory approximations.6

This research helps scientists learn Earth’s internal chemistry.

It’s also, I think, interesting because diamonds are comparatively rare and sparkly; and have inspired a lot of colorful tales.7

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About Brian H. Gill

I'm a sixty-something married guy with six kids, four surviving, in a small central Minnesota town. I mostly write and make digital art. I'm only interested in three things: that which exists within the universe; that which exists beyond; and that which might exist.

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